Solomon wrote all three books. He wrote 3,000 proverbs and 1,005 songs but only 917 proverbs and one song is recorded in the Bible.
Proverbs- a book of wisdom that is meant to be applied to our practical life; the wisdom of God. Proverbs are short statements drawn from long experiences. Proverbs are inspired by and were placed in scripture by the Holy Spirit.
Ecclesiastes- the word ecclesiastes means preacher in greek. The main idea behind this book is how nothing in this life matters outside of God. This book focuses on vanity and how it can take us outside of fellowship with the Lord. Solomon describes personal experiences of attaining things in life but how it was all meaningless; the things of this world can never satisfy the human heart except for the love of Jesus.
Song of Solomon- This is a love song/poem about a married man and woman but it also describes the union between Christ and His redeemed people, the Groom and His bride. This book talks about different types of love: initial, faltering, growing, transforming, and mature love… all the love we experience in our relationship with the Lord.